The invention relates to an apparatus for winding an endless strip (e.g. a film strip to be shown with a projector) in a storage means. In a known apparatus the storage means for the endless strip is in the form of two concentric coils merging directly into each other. From the optical point of view, the coil may be regarded as a solid unit, but from a functional point of view, it is divided into an outer and an inner coil. When the unit is in operation, the inner and outer coils rotate at different r.p.m., respectively depending upon the outgoing and incoming strip. The film-strip, to be guided, for example for projection, through a projector, is brought out of the storage means by the inner turn of the inner coil and, after passing through the projector, is fed to the outer turn of the outer coil. Since the strip brought out, and the strip returned after projection, have the same rate of travel, whereas the inner and outer turns in the storage means are of different diameters, the inner and outer turns must move in different r.p.m. Thus, in the case of the known technique, the inner part of the applied storage means is driven at a speed which differs from that of the outer part thereof. These different speeds are influenced by separate control devices governed by the strip elements brought out.
The disadvantage of this method is that the r.p.m. of the inner and outer coils are governed entirely by the respective inner and outer turns of the two coils. All turns between the inner turn of the inner coil and the outer turn of the outer coil, which increase in diameter, proceeding from the inside to the outside, by a differentially small amount, move at different rotational velocities between those of the inner and outer coils. All turns in the strip-storage means must move past each other at differential amounts of their rotational velocities, which again must produce friction at the surfaces of the strips.
As illustrated in U.S. Pat. No. 3,722,809, two groups of rollers are typically utilized. A group of inwardly inclined rollers carries the end. The two groups of rollers are driven at different speeds. This allows accurate adjustment of only two turns of the coil. These are, of necessity, the inner and outer turns of the stored strip. All other turns lying therebetween will have to execute an additional sliding movement on the rotating rollers. Finally, it is a disadvantage for the turns to have to carry out, in the course of the whole winding procedure, a constant shifting from the outside to the inside over the two groups of rollers. This makes it quite possible for the surfaces of the strip, which in the case of film must be handled with great care, to bear upon each other and be thus damaged. As a result of the inclined arrangement of the two groups of rollers, in addition to the relative horizontal movement between the turns of the strip, there is a second vertical movement. This produces additional friction between the turns of the strip, and the turns thereof suffer additional damage each time the strip passes through the apparatus.
It is, therefore, the object of the invention to provide an apparatus for winding an endless strip in a storage means, such as to avoid any friction between adjacent strips or coils, and to ensure reliability throughout the entire winding procedure and eliminate excessive tensile stresses in the strip.
It is a further object of this invention to provide such an apparatus which is suitable for varying amounts of film.
It is a further object of this invention to provide an apparatus which is structurally simple to produce.